Arsenic is a natural element that occurs in organic and inorganic forms. Considered as less toxic, organic arsenic may occur naturally in many types of foods including some seafood and seaweed products. Once consumed, this organic form of arsenic is quickly eliminated by the body.

The inorganic forms of arsenic, such as arsenate and arsenite have particularly adverse health effects. Found naturally in soil and rock, inorganic arsenic can enter creeks, dams, reservoirs and other sources of water supply by wind-blown dust, industrial operations including mining and smelting, erosion of natural deposits and natural disasters including bush fires and flooding.

Due to its level of toxicity, inorganic arsenic has been used as a wood preservative and for controlling in timber the presence of insects including termites, bacteria and fungi. Arsenic has also been used in the manufacturing of insecticides, poisons and weed killers.